Solar hot water systems are capable of supplying hot water in a manner that is relatively cheaper than conventional electrical or gas fired systems. However, most systems of this type do not rely solely on solar heating and usually incorporate a separate booster system, in order to heat the water to the required temperature when prevailing conditions prohibit heating by solar power alone.
Largely due to regulatory provisions, such systems must include safety devices to operate in the event of some fault. For example, should a short circuit occur such that the controller does not disable the heating element, a safety switch is provided that will disable the heating element when a predetermined temperature is exceeded. A qualified electrician can then be called in to correct the fault and reset the system.
However, in some hot regions, it is common for water to be heated by the solar system to a temperature exceeding a predetermined safe level, such that a safety mechanism in the electrical heating system will trip out and disable the heating element. Such a safety mechanism generally operates only on the basis of sensed water temperature and does not allow differentiation between overheating due to solar heating and overheating due to a fault in the electrical system. For this reason, when a safety mechanism trips out, safety considerations have, to date, dictated that a qualified electrician check the system and, where appropriate, reset the system. That is, even if a safety mechanism trips out due to the prevailing conditions, and not due to an electrical fault, the average consumer is not able to reset the system and maintain a constant hot water supply. Rather a qualified electrician must be called, even if no electrical fault exists.
For this reason, hot water systems to date have been designed to facilitate the electrician's job and generally reset switches are located in the vicinity of solar heating equipment on the roof of a building incorporating the equipment.
This arrangement may be undesirable for the consumer. For example, where climatic conditions alone have caused overheating of the system, such that the safety mechanism has operated to disable the heating element, the safety mechanism has usually tripped out during daylight hours. This tripping is unlikely to be detected by the user until the system falls below the minimum operating temperature at which the electrical heating system must be utilised to maintain the system operating temperature. This may not be detected until the following evening and could result in the system, not re-heating to operating temperature. It is at this point, when the water is no longer at the operating temperature, that the qualified electrician is called. There is then a further delay until the electrician is able to reset the system, which causes the water temperature to fall further, and thereby increases the time delay until the water is again at the desired operating temperature.
This is a particular problem in isolated locations, such as the outback of Australia, where a qualified electrician is neither nearby or easily accessible.
This type of problem is not only restricted to solar hot water systems. In electric storage systems, it is common for the safety circuit to trip out due to a fault on the electricity supply line or some other fault unrelated to the electric heating circuit. Such a fault may, for example, be a power surge or a spike. With the increased use of sophisticated electronic safety switches power surges and spikes cause false tripping to be a regular problem. As with the solar hot water systems, these false trips prevent the hot water system from supplying water at operating temperature. They also decrease energy efficiency due to the cooling of already heated water, requiring re-heating and additional energy costs.
Further, with the increasing need to improve the efficiency of energy utilisation comes the need to improve the efficiency of the manner in which hot water systems attain their operating temperature when required.
Commonly, hot water systems maintain the water at the required operating temperature during periods when the demand for hot water is minimal. They use a simple thermostat device that cycles a heater on and off, thereby maintaining the water at the desired operating temperatures. This is inherently inefficient both from an economic and an energy view point, especially during peak electricity demand times.
One manner of dealing with this efficiency problem has been to utilise off-peak electricity, although this may not always be available. However, this can be inconvenient in that the user is strictly tied to off-peak electricity demand times and this is often inappropriate or inconvenient to the user, depending on their particular circumstances.
Another way in which these efficiency issues have been addressed has been to use solar hot water systems. However, these systems also have their drawbacks.
During winter, the periods of sunlight may be insufficient to heat the water to operating temperatures, leaving the system unable to supply water at the desired temperature when required.
To overcome this problem, solar hot water systems use booster heaters and, as in the case of electrical hot water systems, this system can be expensive in that external power is required and inefficient in that water is maintained at a high operating temperature during periods when not essential.
These systems have further drawbacks as it is common for the systems to be maintained below operating temperature. This problem arises because the electrical heating system and the solar heating system are independent.
It is therefore an object of the present invention to provide a system to allow non qualified persons to reset hot water systems when non electrical faults have occurred.
It is also a further object of the present invention to provide a hot water supply system which efficiently and reliably supplies hot water operating temperature only when it is required.